Machine Learning in Football · 06
A coin flip that isn't
A penalty looks like luck and feels like nerve. Read it as a game and it becomes a 3×3 grid: the shooter picks a side, the keeper picks a side, and a goal or a save falls out of whether they match. This time the data records which way the keeper actually dives — so we can finally play out the whole game, not just the shooter's half of it. Five acts on World Cup shootouts, then take the gloves yourself.
Every World Cup shootout kick, 1982–2022
Each dot is one kick, dropped into the part of the goal it was struck — saved or scored. The corners glow, the middle is sparse. Hold that picture: the rest of the piece is about what the keeper does while the ball is on its way.
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The keeper's coin flip
The keeper picks a side before the ball is struck — and is wrong more than half the time
A penalty leaves the spot too fast to react to, so keepers commit early and essentially guess. Across these shootouts they read the correct side on just — of kicks. Here's what that guess is worth.
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Guessing the right side doesn't save the penalty — it just turns a near-certain goal into a coin flip.
The payoff matrix
Shooter picks a side, keeper picks a side — the goal rate falls out of the grid
The whole game on one chart: rows are where the ball went, columns are where the keeper dived, each cell is how often it scored. The outlined diagonal is where the keeper guessed right. Step one cell off it and the penalty is all but in.
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The keeper's only winning move is to guess the shooter's exact side. Everything else is a goal.
Is anyone playing Nash?
If shooters are at equilibrium, every side they use should score equally
Game theory's one clean prediction: at a mixed-strategy equilibrium, every option you play must pay the same — otherwise you'd shift toward the better one. So do left, centre and right convert equally? (Chiappori, Levitt & Groseclose 2002; Palacios-Huerta 2003.)
| Shot side | N | Used | Conversion | 95% CI |
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The abandoned centre
Nobody trusts the middle — which is exactly why it pays
Keepers almost always dive: they stay central on only — of kicks. So a ball hit straight down the middle usually meets thin air where the keeper just left.
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A panenka isn't arrogance — it's reading that the keeper has already decided to dive.
You're the keeper
Five kicks. Real World Cup placements. Commit before it's struck.
Each kick is a real shootout penalty from the data. Pick your dive before the ball goes. Guess the wrong side and it's a goal; guess right and you still have to reach it — a strike into the top corner beats you even when you read it.
The pressure cooker
Does the shootout get scarier deeper in — or do nerves not show up in the numbers?
Conversion by the taker's order number, with 95% CIs, plus the must-score elimination kicks. If pressure bites, it should bite here.
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